The utilization of tamper-proof caps on containers is well known in the art. A particularly ubiquitous tamper-proof package is one which has a container with a threaded neck and an outwardly extending flange beneath the neck threads. The cap screws onto the container threads and has a sealing ring which overlaps the container flange. The sealing ring is attached to the cap by a plurality of perpendicular webs or ribs which form a shear zone whih is fracturable. In operation, opening torque is applied to the cap causing the shearing of the webs or ribs as the cap moves away from the sealing ring which is held fast by the container flange. Once the cap is removed from the container, it is easy for the user to see that the sealing ring has been separated from the cap and that the container has had a previous opening.
While this type of package does give indication of tampering, it is not without serious drawbacks. In many instances the user of the package will be an enfeebled person suffering from arthritis or other ailments and will not be able to apply sufficient torque to both shear the webs or ribs and to overcome the resistance to opening of the tightened cap. The only recourse in this situation is for the user to cut the webs or ribs with a sharp instrument such as a knife. After the webs or ribs have been sheared, then even the enfeebled person is able to loosen the tightened cap. It is the combination of torque required to shear the webs or ribs and to overcome the resistance of opening a tightened cap which has been found to produce this undesirable difficulty.
It is therefore an object of this invention to provide a tamper-proof cap which utilizes easily viewable, fracturable webs or ribs to indicate tampering but which, at the same time, does not require the user to shear these webs or ribs until after initial loosening of the tightened cap.